Driving a fast car on a good track is maximum fun. There is nothing more exhilarating than whistling down the straight away into a tight turn. It gets a whole lot more exhilarating and a lot less fun when your brakes mush out on you. Brakes are such an essential component of performance driving, yet most people consider them as one of the last things to upgrade. Let’s look at this important element and what can be done to enhance their performance.
These are the most visible through the teeny weenie spokes on alloy wheels. Red seems to be the color of choice for the calipers of most performance brake manufacturers, and why not, you paid a bunch for the upgrade so why not show them off! But the fact they are painted is a good thing; we’ll get back to that in a bit.
Factory calipers are typically cast iron, whereas aftermarket calipers are aluminum. The material change is excellent for two reasons, weight and heat transfer. Weight because it reduces unsprung mass allowing the suspension to be more responsive to bumps and dips because of the lower mass.
Better heat transfer is crucial to allow the heat buildup to be dissipated quickly. A caliper loses heat through three methods: conduction, convection, and radiation. Conduction is via the surrounding mounting structure or through the brake fluid. Convection is the wind whistling past the hot surface and the last method; radiating heat via the caliper emitting heat in the infrared spectrum to other cooler surrounding components. The first two, convection and radiation, are easy to understand but the emitting or emissivity, as we gear heads call it; can be significant especially when the caliper is hot.
This is where the painting of the caliper is important. A bare aluminum surface has an emissivity of around .10, while a painted surface is more like .95 (irrespective of color). That’s a huge difference in its ability to transfer heat in the infrared area of the spectrum. So painting the caliper red is cool on two levels.
Number of Pistons
Why are calipers made with multiple pistons? It is basic physics; more area distributed over more pad area than stock equals more clamping force needed. Large calipers are typically six-pistons, this is because the pad area is large too. In combination, it creates a more braking force. Stock calipers are a compromise between the cost to make the part and the duty it is likely to see. What works well in normal driving conditions can be disappointing on the track where the force needed to slow down from over 100 mph can be staggering. Your factory brakes that stopped on the freeway are now in a new reality where bigger is better. More piston area, more sweep area, more pad area are things that differentiate high-performance brakes from “street” brakes.
There are a lot of choices when it comes to brake pads. It all comes down to how hard you plan on driving your car. Here are some of the factors to consider:
• Stopping performance when the brakes are cold: How well does the pad grip during the first use? Some pads need to warm with a couple of hard breaking stops before they start working well.
• Stopping performance when the brakes are hot: How well does the pad react in higher temperature such as a windy down hill road, the track or autocross course?
• Pad Life: What kind of miles can I drive before they need replacing?
• Rotor Life: Do the pads really use up and wear away the rotor fast?
• Noise: Some pads squeal which is annoying.
• Dust: A lot or a little and can it be easily cleaned off?
All of these choices will impact cost and performance so consider the type of driving you will be doing most and pick the brake pads for the job.
The selection of the right rotors for the driving you will be doing has similar considerations just like choosing the right pad material. There are several choices for rotors; un-drilled, cross-drilled and slotted. Rotor diameter is significant too. Increasing the rotor diameter over the stock size is important in that it gives you more brake area and better mechanical advantage. Let’s look at the differences to see what makes sense. (We will be discussing only vented rotors.)
Un-drilled rotors are the most common. Structurally they are the most stable and handle the stresses best. That is because they have no drilling through the rotor or milling done to the surface.
Cross-drilled rotors are slick looking. The purpose of drilling is to allow the gasses that can build up from the hot pad surface to vent. They also reduce the mass for a slight reduction in un-sprung weight (mass) as well as rotating mass. The slight disadvantage of drilling holes is that they provide a potential point where stress can concentrate and possibly cause rotor cracking.
Slotted rotors do a similar function to cross-drilling and that is to provide a surface slot instead of a hole to vent gasses which can be generated during extreme braking. Also, they are less prone to stress concentration and therefore more resistant to rotor cracks. The slots also help to wipe away the pad material that is created through the friction of braking.
Time to Consider an Upgrade?
If you are looking to improve the brakes on your C2-C3 Corvette SpeedDirect offers an excellent option. We have adapted the Corvette C6-Z06 brakes to the early Vettes, giving you a number of advantages over the stock brakes, which are:
• Six piston all aluminum Corvette C6 Z06 brake calipers.
• Hawk HP Plus high performance brake pads.
• 13″ cross drilled, slotted or plain rotors.
• Aluminum front rotor hats (The rotor mounts to these).
• Stainless steel braided brake lines.
All the components have been selected to provide what we feel is the best all around value and performance that will modernize the brakes on an already great car.